Document reference [1] mentioned at the end of the description describes a method for making an X-ray imagery device. As illustrated in FIG. 1, this imagery device comprises a matrix of pixels made of a semiconducting material, to convert incident X photons into electrical charges. This semiconducting material is deposited on a panel to read the electrical charges based on silicon 11, comprising several electronic devices each integrated into one pixel of the matrix 12.
This manufacturing method consists of a CSVT (Closed-Spaced Vapor Transport) transfer of the semiconducting material onto a silicon-based substrate integrating electronic devices.
As illustrated in FIG. 2, a source 21 comprising the semiconducting material 22, that may be solid or in powder form, is heated to a temperature T1 of the order of 600° C. The semiconducting material used as the source (CdTe, PbI2, HgI2) is close to substrate 23 (1 to 10 mm). The temperature of the substrate is regulated to a temperature T2 less than T1. It varies from 200° C. to 600° C. depending on the nature of the semiconducting material used and the required quality of the layer. The temperature gradient created enables material transport between the source 21 and the substrate 23. The physical properties of the semiconducting materials used associated with use of the CSVT method make it possible to impose a temperature (200° C. to 450° C.) compatible with the temperature resistance of electronic devices, on the substrate.
The dimensions of the X-ray imagery device thus obtained can vary from a few centimetres×a few centimeters up to 40 centimetres×40 centimeters. In particular, it may be used for medical imagery; it can operate in radiography mode or in radioscopy mode.
In one such device, the surface of the substrate on which the semiconducting material is deposited is heterogeneous. As illustrated in FIG. 3, the surface of this substrate 31 may be amorphous, recrystallised amorphous, polycrystalline or monocrystalline, and is composed of a passivation layer 32 (SiOx or SiN, or SiOx+SiN) in which the openings leave the metallic surfaces 33 (aluminium or another metal) free, for pixellisation of each matrix. The semiconducting material must be in electrical contact with these metallic surfaces and be bonded to them.
Therefore, the semiconducting material is deposited on a surface comprising areas with different chemical compositions. The chemical affinity between the materials from which these zones are made and the semiconducting material to be deposited depends on deposition conditions. Obtaining a good chemical affinity, that guarantees good bond between the silicon substrate and the semiconducting material, imposes deposition conditions; temperatures T1 and T2, growth rate, temperature history, all have an influence on physical properties of the semiconducting material. The physical properties thus obtained are not necessarily compatible with the properties required for the detection of radiation.
Therefore, there is a bond problem between the surface of the silicon substrate and the semiconducting material.
The purpose of the invention is to solve this type of bond problem.